The present invention relates to a process for manufacturing devices that carry an active material, particularly on a lateral edge thereof, based on the deposition of a low-melting alloy.
Numerous applications are known in the prior art which require that inside a manufactured product a material is introduced having a specific activity necessary for the correct functioning of the manufactured product itself. Of particular significance among these applications is the production of lamps, so that in the following description reference is made to devices used in gas lamps, keeping in mind, however, that the process according to the invention can also be utilized advantageously to manufacture devices for different uses.
In the gas lamps industry it is known that various active materials have to be introduced into the lamp, e.g., compounds for mercury release, amalgams for the pressure control of that element in the case of fluorescent lamps, getter materials for the removal of undesired gases from the internal atmosphere of the lamp, which may damage the functioning thereof, or materials emitting particular gases, such as oxygen. The use of these materials, as well as the devices that allow their introduction into the lamps, are the subject of numerous patent documents, such as U.S. Pat. Nos. 3,764,842; 3,794,402; 4,056,750; 4,182,971; 4,278,908; 4,282,455; 4,542,319; 4,754,193; and 4,823,047; and Japanese patent application publications A-60-193253; A-06-096728 and A-06-076796, all relating to devices for introducing inside lamps elemental mercury or a material capable of releasing this element; U.S. Pat. Nos. 3,525,009; 4,461,981 and 4,855,643, all relating to getter devices for the use in lamps; U.S. Pat. Nos. 5,825,127 and 6,043,603 and European patent application publication EP-A-0359724, all relating to devices that combine both the functions of mercury release and gettering integrated to each other; U.S. Pat. No. 5,789,855 and U.S. Pat. No. 5,798,618 both relating to amalgams for mercury pressure control inside the lamp; and U.S. Pat. Nos. 3,519,864 and 6,169,361, both relating to devices for oxygen release inside of lamps.
The devices described in these patent documents are generally manufactured by introducing the active material in a container or by applying it on the surface of a support, and then by fixing the container or support to an adequate prop, which is then mounted in a pre-determined position in the lamp.
However, the manufacturing of these devices is generally rather complex, requiring the mechanical shaping of (generally metallic) small size parts and the assembly of these to each other in various ways. The problem becomes even more serious when considering the present tendency in the lamp industry to miniaturization, which imposes that the above-mentioned devices also be miniaturized. Furthermore, this miniaturization also involves a greater control, both geometrical and dimensional, of these devices, because in the finished lamp these are all arranged in the same zone (the terminal portion of the lamp or at most the two terminal portions in the case of tubular lamps), while avoiding having these devices come into contact with the electrodes or their supports. A contact of this type could in fact change the lamp functioning. Moreover, adopting production processes in which the device is manufactured by assembling (mechanically or through welding) pre-formed parts results in a reproducibility problem as to the shape and size of the finished devices.
Another problem that arises in the production of the devices, made more serious by the miniaturization thereof, is that in some instances it is possible to have particularly delicate manufacturing steps that imply a possible risk of compromising the semi-manufactured product. For example, in the case in which a device must be manufactured having an amalgam for the mercury pressure control, introducing the amalgam into (or affixing onto) the final piece turns out to be a complex operation, which requires the mechanical moving of a piece, generally having a non-planar shape. In contrast, working a part already having the amalgam thereon, e.g., performing a welding between this part and its support, may compromise the adhesion of the amalgam itself on the part. Finally, all these construction problems result in relatively high costs of the devices, especially when compared to the low selling price of the lamps, such that their use is often limited by economic reasons.